Microeconomics, branch of economics that studies the behaviour of individual consumers and firms. Unlike macroeconomics, which attempts to understand how the collective behaviour of individual agents shapes aggregate economic outcomes, microeconomics focuses on the detailed study of the agents themselves, by using rigorous mathematical techniques to better describe and understand the decision-making mechanisms involved.

The branch of microeconomics that deals with household behaviour is called consumer theory. Consumer theory is built on the concept of utility: the economic measure of happiness, which increases as consumption of certain goods increases. What consumers want to consume is captured by their utility function, which measures the happiness derived from consuming a set of goods. Consumers, however, are also bound by a budget constraint, which limits the number or kinds of goods and services they can purchase. The consumers are modeled as utility maximizers: they will try to purchase the optimal number of goods that maximizes their utility, given their budget.

The branch of microeconomics that deals with firm behaviour is called producer theory. Producer theory views firms as entities that turn inputs—such as capital, land, and labour—into output by using a certain level of technology. Input prices and availability, as well as the level of production technology, bind firms to a certain production capacity. The goal of the firm is to produce the amount of output that maximizes its profits, subject to its input and technology constraints.

Consumers and firms interact with each other across several markets. One such market is the goods market, in which firms make up the supply side and consumers who buy their products make up the demand side. Different goods market structures require microeconomists to adopt different modeling strategies. For example, a firm operating as a monopoly will face different constraints than a firm operating with many competitors in a competitive market. The microeconomist must therefore take the structure of the goods market into account when describing a firm’s behaviour.

Microeconomists constantly strive to improve the accuracy of their models of consumer and firm behaviour. On the consumer side, their efforts include rigorous mathematical modeling of utility that incorporates altruism, habit formation, and other behavioral influences on decision making. Behavioral economics is a field within microeconomics that crosses interdisciplinary boundaries to study the psychological, social, and cognitive aspects of individual decision making by using sophisticated mathematical models and natural experiments.

On the producer side, industrial organization has grown into a field within microeconomics that focuses on the detailed study of the structure of firms and how they operate in different markets. Labour economics, another field of microeconomics, studies the interactions of workers and firms in the labour market.

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